Amphioxus long has been of interest to zoologists searching for a vertebrate ancestor. Explain why amphioxus captured such interest and why it no longer is considered to resemble closely the most recent common ancestor of all vertebrates.

Amphioxus is unlike the closest living relative of vertebrates, but are different because they lack a triparite brain, chambered heart, specialized sensory organs, muscular gut and pharynx, and neural crest tissue.